Releasable latch member for electric circuit breaker



M' h 28, 1967 D. B. POWELL RELEASABLE LATCH MEMBER FOR ELECTRIC CIRCUIT BREAKER Filed 001;. 22, 1964 IN VENTOR. DA W0 5. Poweu.

A TTORNEY United States Patent I RELEASABLE LATCH MEMBER FOR ELECTRIC My invention relates to electric circuit breakers, and

more particularly, to electric circuit breakers of the type including a pivotally mounted releasable support normally supporting one end of an operating spring, and releasable to cause automatic opening of the circuit breaker.

In electric circuit breakers of the type described, the releasable support member referred to, according to the prior art, has ordinarily been provided by a flat metal stamping having a separate piece of either metallic or molded insulation material attached thereto to provide a pivotal support, Such prior art structures have included disadvantages of either relatively high cost or difiiculty of assembly or lack of stability and hence reliability.

It is an object of the present invention to provide an electric circuit breaker of the type described including a releasable supporting member which is simple, dependable, and requires no sub-assembly operations.

It is a further object of the inventionato provide an electric circuit breaker of the type described including a releasable support member which is formed from a single flat stamping pieceand which includes integral pivotal support portions.

It is another object of the invention to provide a circuit breaker of the type described which includes a releasable support member wherein the releasable support member permits the operating spring to assume a position, when the parts .are in the =on" condition, such that its line of action passes closer to the pivotal axis of the .releasable support than is possible with prior art struc- -member formed of a single piece of flat sheet metallic material having a first transverse generally planar portion having outwardly-directed pivot lugs thereon, and an integral main body portion extending substantially at right angles to said transverse portion, and being joined thereto by a bend substantially midway between said outwardly-directed pivotal support lugs. The releasable support member further includes an embossed strengthening rib diagonally of the transverse body portion and an integral generally conical deformed portion in the transverse portion substantially midWay between the outwardly-directed lug portions providing clearance for the operating spring.

FIGURE 1 is a side elevation view of an electric circuit breaker incorporating the invention, the side of the insulating casing nearest the observer being removed, and the parts being shown in the oif position;

FIGURE 2 is a view of the operating mechanism similar to that of FIGURE 1, the parts being shown in the on position;

FIGURE 2A is a side elevation of a portion of the mechanism of FIGURE 1, and

FIGURE 3 is a perspective view of the releasable support member of the circuit breaker of FIGURE 1.

The invention is shown in FIGURE 1 as incorporated in an electric circuit breaker including a generally rectangular insulating casing made up of two cooperating 3,311,724 Patented Mar. 28, 1967 generally tray-shaped halves joined together by suitable means such as by rivets 11.

A stationary contact 12 is carried by a portion of a plug-in type socket member 12A. A movable contact 13 is carried by a movable contact :arm 14 which is bifurcated, and has the ends of the bifurcated portions pivotally supported on the lower end of an insulating handle member 15, at pivot point 161' The handle 15 is pivotally supported in the insulating casing on integral pivotal support 17.

The contact arm 14 has a tension type operating spring 18 connected to the bight portion thereof, by means as shown in FIGURE 2. The upper end of the operating spring 18 is anchored in a hole 19 in the releasable support member 20. Pivotal movement of the handle member 15 about its pivotal support therefore moves the pivot 16 of the contact arm back and forth across the line of action of the main operating spring 18.

The releasable support member 20 is pivotally supported in the casing by means of outwardly projecting lug portions 21 which are received in generally V-shaped pockets or recesses 22 in the casing halves. The main body portion of the releasable member '20 terminates in a latchable portion 23 which is normally held by a latch projection 24 of a combined-latch and armature member 25. The latch-armature member 25 is pivotally supported in the casing adjacent to its upper end by integral lugs 26 received in corresponding pockets, not shown, in the insulating casing halves. The latch-armature member 25 is biased toward latching position by a compression spring 27.

An elongated bimetallic strip member 29 is rigidly mounted at one end on a terminal strap 30 which is securely anchored to the base by suitable means such as by a mounting screw 31. The terminal strap 30'carries a connecting screw 32 adjacent its outerend, and the inner end thereof is adjustably positioned by a calibrating screw 33 which is threadedly carried by a nut 34 trapped in the insulating casing. The bimetallic strip 29 carries a generally U-shaped magnet field piece 35 at an intermediate portion thereof and the lower end thereof acts on a return-bent portion 25A of the latch-armature member 25.

Heating of the bimetallic member such as 'by excess current passing therethrough, causes it to deflectso as to move its lower end to the right as viewed, moving the latch-armature member counterclockwise about its pivot 26 and withdrawing the latch member 24 from the latchable portion 23 of the releasable member 20.

The lower end of the bimetallic strip 29 is connected by a flexible conductor or braid 36 to the contact arm 14. The current path through the circuit breaker in the closed position, therefore, is as follows. From the line terminal or socket 12A to the stationary contact member 12 to the movable contact member 13, to the contact arm 14, through the braid 36 to the bimetallic strip 29, to the terminal strap 30, to the terminal 32.

To move the circuit breaker parts from the off position of FIGURE 1, the handle 15 is rotated in counterclockwise direction, moving the pivot point 16 of the contact arm 14 to the right as viewed. When this point passes across the line of action of the operating spring 18, the contact arm 14 moves clockwise about the pivot point 16 with a snap action to the closed circuit position as shown in FIGURE 2. Opening action of the circuit breaker takes place in reverse fashion.

When the parts are in the position as shown in FIG- URE 2, an excess overload or short circuit causes release of the latch member 24 from the portion 23 of the releasable member 20. The downward pull of the tension spring 18 exerted on the releasable member 20 causes it to rotate clockwise about its pivotal support 22 until the line of action of the spring 18 passes across the pivot point 16 of the contact arm 14. When this occurs, the contact arm 14 moves counterclockwise about its pivotal support 16 to open circuit position automatically. This movement takes place regardless of whether the handle 15 is manually retained in the on position.

On the occurrence of extremely high overloads or short circuit currents, the magnetic field piece 35 acts to attract the latch-armature piece 25 to it, causing release of the latch member 24.

In accordance with the invention, the releasable support member 20 is constructed as shown in FIGURE 3, from a single piece of fiat sheet metallic material, and includes a generally planar transverse portion 40, and a generally planar body portion 41, the plane of the body portion 41 extending substantially at right angles to the plane of the transverse portion 40. The plane of the body portion 41 also substantially bisects the line between the lugs 21, and is bent from the same piece of material. In addition, the piece 20 is strengthened by the provision of a diagonal embossed rib 43 in the transversely extending portion 40.

For the purpose of facilitating resetting of the releasable member, the portion 40 includes a laced-out portion 42 alfording a radiused cam surface on which the end portion 15A of one of the depending side portions of the handle acts. Thus when the handle is moved to the off position as in FIGURE 1, the end portion 15A engages the surface 42 and rotates the member 20 counterclockwise to reset position. 7

For the purpose of providing clearance for the spring '18, a portion 44 is deformed in conical shape from the transverse planar portion 40.

As indicated particularly in FIGURE 2A, it will be observed that since the .portion 44 is deformed out of the plane of the piece 40, it permits the line of action of the spring 18 to extend extremely close to the pivotal axis of the piece 20, which extends between the lower edges of the lugs 21 (distance D in FIGURE 2A). This is important since the distance between the line of action of the spring .18 and the pivot of the piece 20 determines the portion of the force of spring 18 which tends to rotate the releasable member 20 clockwise, and therefore causes pressure on the latch member 24. For reliability of calibration or adjustment, it is generally desirable to keep such latch pressure low. Accordingly, it is desirable that only a small portion of the force of spring 18 should act to cause such latch pressure, and a relatively large portion act to cause contact pressure.

While the invention has been shown in one particular embodiment, it will be readily apparent that many modifications thereof 'may be made. It is therefore intended by the appended claims to cover all such modifications as fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent-of the United States is:

1. An electric circuit breaker comprising:

(a) an insulating casing,

(e) a contact arm pivotally connected to said manually operable handle at one point and connected to operate said relatively movable contact at another point,

(f) a releasable support member pivotally supported in said insulating casing at a first point and having a latchable portion at a second point,

(g) a tension type operating spring interconnecting said contact armand said releasable support member so that movement of said manually operable member about its pivotal support in said casing moves the pivotal support of said contact arm across the line of action of said operating spring to move said. relatively movable contact into and out of engagement with said relatively stationary contact with a snap action,

(h) said releasable support member being constructed of a single flat sheet of metallic material and comprising a first generally planar transversely extending portion, said transversely extending portion including a pair of opposed edge portions providing said pivotal support of said member in said casing and'a generally planar body portion bent from said sheet substantially at right angles to said transversely extending portion and substantially midway between said bearing portions, said operating spring being connected to said body portion of said releasable support member between said transversely extending portion and said latch portion.

2. An electric circuit breaker as set forth in claim 1 wherein said transversely extending portion of said releasable support member includes a conically deformed integral portion substantially midway between said opposed bearing portions and providing clearance for a por- .tion of said operating spring, whereby the line of action of said operating'spring can extend extremely close to the said pivotal support of said releasable support member.

References Cited by the Examiner UNITED STATES PATENTS 2,204,409 6/1940 Gano.

2,769,049 10/1956 Edmunds.

3,088,088 4/1963 Gelzheiser.

3,213,220 10/1965 Powell 200-116 BERNARD A. GILHEANY, Primary Examiner.

H. B. GILSON, Assistant Examiner. 

1. AN ELECTRIC CIRCUIT BREAKER COMPRISING: (A) AN INSULATING CASING, (B) A RELATIVELY STATIONARY CONTACT MOUNTED IN SAID INSULATING CASING, (C) A RELATIVELY MOVABLE CONTACT MOUNTED IN SAID INSULATING CASING, (D) OPERATING MECHANISM FOR MOVING SAID RELATIVELY MOVABLE CONTACT INTO AND OUT OF ENGAGEMENT WITH SAID RELATIVELY STATIONARY CONTACT COMPRISING A MANUALLY ENGAGEABLE HANDLE MEMBER PIVOTALLY SUPPORTED IN SAID INSULATING CASING (E) A CONTACT ARM PIVOTALLY CONNECTED TO SAID MANUALLY OPERABLE HANDLE AT ONE POINT AND CONNECTED TO OPERATE SAID RELATIVELY MOVABLE CONTACT AT ANOTHER POINT, (F) A RELEASABLE SUPPORT MEMBER PIVOTALLY SUPPORTED IN SAID INSULATING CASING AT A FIRST POINT AND HAVING A LATCHABLE PORTION AT A SECOND POINT, (G) A TENSION TYPE OPERATING SPRING INTERCONNECTING SAID CONTACT ARM AND SAID RELEASABLE SUPPORT MEMBER SO THAT MOVEMENT OF SAID MANUALLY OPERABLE MEMBER ABOUT ITS PIVOTAL SUPPORT IN SAID CASING MOVES THE PIVOTAL SUPPORT OF SAID CONTACT ARM ACROSS THE LINE OF ACTION OF SAID OPERATING SPRING TO MOVE SAID RELATIVELY MOVABLE CONTACT INTO AND OUT OF ENGAGEMENT WITH SAID RELATIVELY STATIONARY CONTACT WITH A SNAP ACTION, (H) SAID RELEALSABLE SUPPORT MEMBER BEING CONSTRUCTED OF A SINGLE FLAT SHEET OF METALLIC MATERIAL AND COMPRISING A FIRST GENERALLY PLANAR TRANSVERSELY EXTENDING PORTION, SAID TRANSVERSELY EXTENDING PORTION INCLUDING A PAIR OF OPPOSED EDGE PORTIONS PROVIDING SAID PIVOTAL SUPPORT OF SAID MEMBER IN SAID CASING AND A GENERALLY PLANAR BODY PORTION BENT FROM SAID SHEET SUBSTANTIALLY AT RIGHT ANGLES TO SID TRANSVERSELY EXTENDING PORTION AND SUBSTANTIALLY MIDWAY BETWEEN SAID BEARING PORTIONS, SAID OPERATING SPRIN BEING CONNECTED TO SAID BODY PORTION OF SAID RELEASABLE SUPPORT MEMBER BETWEEN SAID TRANSVERSELY EXTENDING PORTION AND SAID LATCH PORTION. 